Pens used with ink-jet printing systems available today include print heads which have nozzle arrays with very small nozzles through which ink droplets are fired. The ink used with the pens typically dries quickly, permitting plain paper printing. Such pens are susceptible to nozzle clogging with dried ink or minute particles such as paper fibers.
Ink-jet printers have utilized a service station which includes a mechanism to cap the print head nozzles when the pen is not printing. Typically, the cap mechanism encloses the exposed outer surface of the orifice plate defining the nozzle array, to help prevent drying of the ink at the nozzles, and prevent contact with dust. The service station may also include a wiper mechanism for wiping away particles accumulated on the orifice plate, and a receptacle into which the pen periodically fires to purge dried or plugged nozzles.
In a multi-function office machine marketed by Hewlett-Packard Company as the 500 Series "OfficeJet," the service station includes a sled to which are affixed rubber caps to serve the capping function. A motor driven rotating cam engages the sled, when the carriage is positioned at the service station, to lift the sled and its datum surfaces into engagement with the carriage. As the datum surface engage the corresponding carriage datum surfaces, the rubber caps are brought into engagement with the nozzle arrays of the print cartridges mounted in the carriage. This arrangement is a single stage capping mechanism.
This invention provides an improved two-stage capping technique for capping the nozzle arrays of an ink-jet printing system.